Stroboscopic timing and testing of diesel and similar engines



March 14, 1944.

H. M. FULLER STROBOSCdPIC TIMING AND TESTING OF DIESEL AND SIMILAR ENGINES Filed Nov. 8,

1940 4 Sheets-Sheet 1 Inventor flow/42p M- 771M. 2

A itorney March 14, 1944. H. M. FULLER 2,344,037

STROBOSCOPIC TIMING AND TESTING OF DIESEL AND SIMILAR ENGINES Filed Nov. 8, 1940 -4 Sheets-Shet 2 j 25 I Inventor #omwap M 7711.457?

r36 By a o A fiorrzey Mmh 14,1944; I -l. M. FULLER 2,344,037

STROBOSCOIIC TIMING AND TESTING 01:, DIESEL AND SIMILAR ENGINES Filed Nov. 8, 1940 4 Sheets-Sheet 3 I; s t

:3] Inventor Won 42D M TaLLER D SIMILAR ENGINES March 14, 1944. H. M. FULLER STROBOSCOPIC T-IMING AND TESTING OF DIESEL AN Filed Nov. 8 1940 4 Sheets-Sheet 4 A itomeg of the Diesel engine cycle whereby Patented Mar. 14, 1944 2,344,037 STBOBOSCOPIC' TIMING AND TESTING F IESEL AND SIMILAR ENGINES Howard M. Fuller, Saratoga Springs, N. Y.

8,11940,.Serial No.*364,944 1 1 Claim. (Chill-311') Application November My invention relates to method and apparatus for use in testing and timing Diesel engines, and the primary object of my invention is to provide means of the character indicated whose indicators are synchronized with a definite part the operation of a solid fuel injection system of a Diesel engine may be accurately checked while the engine is in actual operation and under load, permitting the fuel injection period to be accurately made.

Another important object of my invention is to provide means of the character indicated whereby the'operating conditions of the injection valve and fuel pump of the Diesel engine checked.

my invention will beapparent from a reading of the following description taken in connection with the appended drawings, poses of illustration 1 have shown preferred embodiments of my invention.

In the drawings:

Figure 1 is a general fragmentary schematic view showing apparatus in accordance with the present invention.

Figure 2 is an enlarged sectional elevational view of the phone-crystal head mounted on and in operative relation to an injection valve of the Diesel engine.

Figure 3 is a top the cover removed.

Figure 4 is a horizontal sectional view taken through the lower part of the head and showing the clamp thereon.

Figure 5 is a side elevational view of the wire which operatively connects the valve stem and the phone-crystal needle.

Figure 6 is a schematic wiring diagram showing the electrical components and connections for the stroboscopic embodiment of the invention.

Figure 7 is a similar schematic wiring diagram of the two-element, neon light embodiment of the invention.

In order to check the fuel injection timing as it actually takes place in the Diesel cycle, it is necessary that the actual time of opening of the fuel injection valve have an indicator on the flywheel of the engine with respect to top dead center of the piston in the particular cylinder under consideration. The normal injection point is about 6 degrees ahead of top dead center on the compression stroke, but this varies with diflerent grades of fuel oil.

plan view of the head with wherein for purj method of vmarking the-fixed pointer, indicated by them, center orinjection point. The engine is known the witness marks on the pump is actually timedcut and try method dead center and the injectionpoints is to provide a fixed pointer 0r witness mark on the engine and the two marks on the flywheel, for each cylinder, one indicating the top dead center position, and the other the injection point. When these marks line up with the engine is in the position namely, either top dead to be in time if line up when the injection point marks on the flywheel lineup with the reference mark or fixed point on the engine. The apparent lining up of these witness marks on the pump and flywheel is a rather uncertain and unsatisfactory method of timingbccause a difference of as little as .005 is hardly noticeable on the pump but produces a difierence in witness marks on the flywheel and bracket 'of about V or about /2 degree inflring timing. These comparisons or lining up of witness marks are performed while the engine is'stopped, so that the only thing that is the position of the pump and not the actual opening of the fuel injection valve. Even when the fuel injection pumps are new this method of timing is more or less a and provides no way of checking the. actual fuel injection point while the engine is in operation.

An essential fact in the discovery and the application of the principles of the present invention is that the fuel injection valves in certain types of Diesel engines open by hydraulic pressure, and are similar in action to a safety valve, the opening thereof being extremely fast and the valve remaining open while the fuel is bein forced into the cylinder, and closing almost as rapidly by spring action. In line with this fact I discovered that by resting a wire on the upper end of the valve stem, any moton of the fuel injection valve itself can be transmitted out of the valve body'to any mechanism with which the wire may be connected without appreciably affecting the action of the valve, if the mechanism is light enough or lacking in inertia. suitable mechanism of this character comp a phono-pickup erystallaid on its side and hav ing a stiff wire held in the needle hole with th wire resting on the upper end of the fuel in jection valve stem, so that any motion of th valve stem is transmitted to the crystal, an this physical motion converted into an E. M. or voltage by the action of the crystal. It

The conventional a important to note that because of the sudden as a sound transmitting or converting device. valve stem as shown. The wire has an ent with the upam lined by tms tube is fed through a 03 d, wire 25 in its operative engasemen con denser and a two conductor shielded cable 18 per end 01' the valve stem 1. in the operatl n f and connectors, to a stroboscopic tube, In t the valve stem. The wire 25 is straight from the c1 me, e 1a m dicated by the numeral 28 around the outer end g ggg izggg g fiz x z pse portion of the still wire 22 and soldered as indi- The stroboscoplc tube is supported near the cated by the numeral 29. The wire 25 is prefnrwhee-l bracket or the cum-ha As the New erably oi spring steel and the still wire 22 also cal connection between the sleeve H and the 3 3;23 2 2 the an 88 is set forth an valve body 8 acts as an electrical ground for the entire apparatus.

arrangement wherein a common two'element Fuel is supplied to the injection valve at a pres sure of approximately 3,000 pounds per square 40 inch through the fuel condu' 34 for injection.

ing the solid injection system using a single fuel as to compres t pring 3. As t valve t valves which comprises the valve body 6 of a on spring I which the pickup wire 25 transmits to held in a vcrtically adJusted position by the adsuch motion. justing screw H which is threaded in the screw The single shielded conductor 30 connects the II. The upper part oi the valve body as indicrystal head with the cabinet which is generally cated by the numeral [3 is reduced to approxldesignated 35, the shielded cable 30 being what mately the same diameter as the nut 12, so that i m on k wn as y t l mike cable. The the nut l2 and the portion l3 snugly accept connecting means 31 are what is commonly the expansible sleeve H which telescopes thereknown as mike connectors. on and has a contractible clamping ring I! whi h The cabinet 36 is in the form of a suitable casis adapted t b ti htened by a, s w Is t k ing enclosing a chassis (not shown) on which is place, The sleeve depends frgm mounted one 110 V. to 350-0-350 V. to 6.3 V. power casing n wh h i horizontally transformer 31, a power on or oil switch 38, a elongated and provided with a removable cover D w r flush plug receptacl 39, one 8-8-8 mid. l8 which is held in place by a screw or bolt is inverted can dry-electrolytic condenser shown in thr d d int th bott [1 sections indicated by the respective numerals 40, On the bottom I1 is supported the phono-crys- 4| 3 011B 20 'y filter Choke 43, on type t l rt i 20 and w h h operativeiy 7 84 rectifier tube and socket 44, one type 6J7G tube to a position at one side or the axis 01' the hole 24 paper condenser (600 volts) 49, and associated in the upper part of the sleeve H as shown in Figresistors. These resistors comprise the 50,000

foregoing resistances rate 1 watt, 2 watt, 1 watt,

/2 watt and 1 watt, respectively. These are supplemented by a 28 henry 50 m. a. choke 58.

The foregoing circuit as shown in Figure 6 is arranged so that the same acts as a detector and amplifier. It is necessary to use shielded cable-as a means of transmitting the electrical impulse generated by the crystal 20 to the chassis of the amplifier or relay, to make the action of the relay and connected light stable. shown the crystal impulse is fed. to the control grid of the tube here designated 45 where there is a megohm resistor 55 across the circuit to provide a load for the crystal and a leak for the grid. Due to the action of the tube 45 and connected resistors, inductance capacity and voltage, the signal or impulse received is amplified or enlarged in amplitude. From the plate circuit ofathe tube 45 the amplified signal is picked off by the action of the .003 mfd. condenser 09.

The condenser 49 allows the signal to pass to the stroboscopic tube 59 through one of the conductors of the shielded cable 60 but keeps the high D. C. voltage used in the amplifier tube out of the stroboscopic control circuit. Upon energizing the control circuit of the stroboscopic tube, the tube discharges the condenser 5| which has built up an electrostatic charge. This condenser is housed in the stroboscopic tube socket and reflector 52. Two-conductor pin type connectors are used for terminals between the amplifier chassis and thetwo-conductor shielded cable, and also between the two-conductor shielded cable and the stroboscopic tube socket and reflector. By proportioning the resistors 53 and 64 so With the circuit as 5 ference has been measured in inches.

plying this by the number of degrees ahead of top dead center that the engine should start to receive the fuel. This gives the position in inches with reference to top dead center, if the circum- The distance shouldbe measured from the top dead center mark 51 onthe bracket 69 and in such a direction from this mark that a point on the fly wheel passes the injection point mark 68 before 10 the same point passes the top dead center mark 51. The conventional marking of a so-called fourecycle engine is one D-C mark on the flywheel for each two cylinders and a 1-? mark also on the flywheel for each cylinder. On two-cycle l5 engines there is one D-C mark on the flywheel for each cylinder and one 1 P mark for each cylinder. l

If the'stroboscopic tube light 59 is held with its shield 1.0 over the moving flywheel in such a manner that anything passing under the light is illuminated'by it, the white marks will appear to be stationary or stopped. Since the light flashes the instant the injection valve opens, the position in the Diesel cycle at which the fuel injection actually takes place is shown with respect to the top dead center. By measuring the distance from the mark 65 to the mark 58 and dividing the distance by the proper constant for the engine, such as 50, the result will. be the thickness of the shims which should be added to that about 95 volts exist between ground and the second grid, the stroboscopic tube may be made 'to flash or fire upon very small crystal movements. The discharge of the condenser 6| through the stroboscopic tube produces a strong light of extremely shortduration. namely, approximately 7 micro seconds. Any moving line, when viewed under a light of only a few micro seconds, appears to stand still and have no motion. This is due to the persistency of vision and is called stroboscopic effect.

Because the time elapsing between the point in time at which the crystal is stressed, i. e., the

valve opens, until the stroboscopic fires is also of the order of micro seconds, the time delay in the crystal amplifier and the stroboscopic may be considered as negligible or the action of the unit may be considered as instantaneous or that the light flashes at the same instant that the fuel injection valve stem starts to move.

- The marks 65 on the flywheel 55 and the marks 01 and 68 on the engine frame bracket 59 consist of white marks on a dark background so arranged that they may be easily seen from the engine room floor. On a six cylinder engine there are three marks on the flywheel, one to indicate the top dead center of each crank position and two marks 51 and 68 on the bracket 69 on the engine frame. When the engine is in position of top dead center, the mark 55 on the flywheel and that on the bracket are laid out so as to line up. The top dead center mark 51 on the bracket is not used after it is once established, because it is only a reference mark for use in establishing the injection point mark 58. The injection point mark 68 is found by dividing the circumference of the flywheel by 360 degrees and multi- 50 tubes to heat to the proper temperature.

or subtracted from the pump tappet to, bring the fuel injection point into proper firing time or re,- lation. When the Diesel engine is firing at the proper time, the witness mark 55 on the flywheel and the witness mark 58 on the bracket 69 coincide. Another cable 10 may be plugged in the box 35 to energize a head phone II to give an audible check on the testing operations.

The head phone H is used only 'in connection with the two-element neon light arrangement which is diagrammed in Figure '7 of the drawings.

Discussion of current flow inFiqure 6 i It will be assumed that the power lead is con- 5 nected to the proper outlet supplied with 115 v.

and that the power has been turned on for sufficient length of time to allow the cathodes of the The circuit discussed will be that of Figure 6.

The action of ,the rectifier circuit to produce a high voltage .source of D. C. power is as follows. Due to the current flowing in the primary of the 55 power transformer 31, magnetism linking the primary, the high voltage secondary, and the filament lighting, .or heating secondary, a voltage is induced in these windings. Because of the check valve action of the rectifier tube 44 current flows through it and its connecting elements in one direction only. By use of 40, ll, 42 andv S /the current passed by the rectifier tube is smothered out so that the potential across 46 has a comparatively smooth wave shape or a comparative constant difference in contrast to pulsating unidirectional current that would flow if they were omitted.

46 provides a small load for the rectifier tube and transformer to prevent damaging peak volt- 70 age developing, also to provide a method of ob- 7s erated across its terminals.

taining D. C. voltages other than the maximum. 46 also acts as a discharge resistor for condenser ll, 42, 40 after the apparatus is shut off.

Upon movement of the crystal a voltage is gen- This causes a can rent to flow through the single conductor cable and resistor 55. This also causes a voltage to exist or fluctuate across the flrrt grid and cathode of tube BJ'IG tube I. If this voltage is of the proper histantaneous polarity it will increase the flow of electrons from the cathode to the plate, or increase plate current. The opposite polarity will cause a decrease in plate current. Resistance 55 also acts as a leak for current from the first grid when this element becomes positiv because of excessive signal fluctuations. Grid two acts as, in most cases, an accelerator for the electrons which have passed through the first grid. It is connected to the high voltage source through 56 and ill. High or signal frequency currents are allowed to pass back to cathode by condensers 48 and 41. Grid 3 acts as a collector for electrons which may be wandering around, due to secondary emission, in the space between plate and grid two. It also acts as a quick action stop for the electron flow. After striking the plate the electrons pass through inductance 58, resistance 54 and 50 to the high voltage source. This path is taken by the D. C. component of the tube current only. The D. C. component of the BJ'ZG tube 45 current also flows from the ground or low voltage side to the oathode through 5|. This current causes the cathode due to 5| to be at a negative or lower voltage than ground.

The A. C. or signal component of plate current due to the low impedance of condenser 49 and the high impedance 58, passes through 49, 51 and 41. The passage of current through 51 causes a voltage to exist across its terminals, one side of which is connected to the control grid of the stroboscopic tube 59. 5'! also acts as a leak for a charge that may build up on the grid of the stroboscopic tube.

The stroboscopic tube 59 is a cold cathode neon tube. It has two grids in addition to a plate and cathode. When connected as shown it has at all times a high voltage across the cathode and plate. The plate as in other tubes being positive. Grid 2 is connected by use of a voltage divider to plate and cathode. The purpose of this divider is to maintain a constant voltage on grid 2, the value of which should never exceed 95 v. between grid and cathode. The purpose is to excite the tube to a point near the flash or firing point. Thus a small voltage applied to the first grid provides enough additional excitation to cause the gas in the tube to ionize and fire between cathode and plate thus discharging condenser 6|. The instantaneous discharge of SI produces a large current flow through the stroboscopic tube. This current due to the neon gas produces an intense light. The duration of this light is very short, approximately 3 micro seconds. 12 is in series with the plate so that the tube will go out upon discharging 6i. Condenser 6| is recharged between intervals of firing.

Thus, upon the slightest movement of the crystal a strong light of very short duration is made to flash in time phase or synchronism with crystal movement. In fact, the light flash has been completed before the crystal has completed its initial movement, and several flashes may occur during a fuel valve opening.

Discussion of current flow in Figure 7 This modification comprises a twoelement neon light arrangement.

It will be assumed that the power lead is connected to the proper outlet supplied with 115 v. A. C. and that the switch is in the on position, and that the power has been turned on for sufflcient length of time to allow the cathodes o! the tubes to heat to the proper temperature.

The action of the rectifier circuit to produce a high voltage source of D C. power is as follows: Due to the current flowing in the primary of the power transformer, magnetism linking the primary, the high voltage secondary and the filament lighting, or heating secondary; a voltage is induced in these windings. Due to the check valve action of the rectifier tube, current flows through it and its connecting elements in one direction only. By use or ll, 42 and 0 the pulsating current passed by the rectifier tube is smothered out so that the potential across I. has a comparatively smooth wave shape or a comparatively constant difference in contrast to pulsating unidirectional current-that would flow if they were omitted.

46 provides a small load for the rectifier tube and transformer to prevent damaging peak voltage developing, also to provide a method of obtaining D. C. voltage other than the maximum. II also acts as a discharge resistor for condenser 4|, 4| 42. after the apparatus is shut off.

Upon movement of the crystal'a voltage is generated across its terminals. This causes a current to flow through the single conductor cable, resistor 55' and condenser 82 in parallel with the resistor. This also causes a voltage to exist or fluctuate acros th first grid and cathode of (LNG tube If this voltage is of the proper polarity it wi l increase the flow of electrons from the cathode to the plate, or increase the plate current. The opposite polarity will cause a decrease in plate current. Resistance also acts as a leak for current from the first grid when this element becomes positive because of excessive signal fluctuations. Grid 2 acts as. as in most cases. an accelerator for the electrons which have passed through the first grid. It is connected to the high voltage source through 56' and 50. High or signal frequency currents are allowed to pass back to cathode by condenser l8 and 41. Grid 8 acts as a collector for electrons which may be wandering around, due to secondary emission, in the space between plate and grid 2. After striking the plate the electrons pass through res stance 54', closed circuit phone jack 1! and phones H if plug is inserted in jack, resistance 50' and then to the high voltage source on rezistance 4B. This path is taken by the D. C. component of the tube current and part of the component. The D. C. component of the tube 45 flows from the ground of low potential side to the cathode through 16. This current causes tl-e cathode, due to II. to be at a positive or higher voltage than ground.

The major part of the A. C. or signal component of plate current du to the comparative low impedance of condenser 49 passes through 49 and 85, and thus to the ground. The passage of current through this resistor causes a voltage to exist across its terminals and thus a voltage exfsts across the control grid and cathode of GLGG tube 88'. This resistor 85' also acts as a leak for a current that may flow if the amplified signal should swing positive or become greater than the voltage across the cathode biasing resistor 8B.

The D. C. component of current in the 6L6G' tube 88' flows similar to that of the 6J7G tube, the exception being that there is no third grid. The current flowing from the cathode is acted upon by the first grid and made to increase or decrease in magnitude as the voltage upon this element chanzes. The second grid as in the previous tube As a signal is impressed on the control grid of acts as an accelerator. The D. C. component of the 6L6G, 88' tube, the plate current is caused to current flows through resistors 89 and 94 and thus increase. This increase in plate current, due to to the high voltage source. The A. C. or signal the high impedance of the inductance and the component is by-passed by condensers 90 and 81, 5 comparatively low impedance of the neon lamp. directly back to the cathode. Upon striking the flows through the neon lamp, causing it to ignite plate the D. C. component of current passes or flash. Thus, upon amovement oi the crystal, throughthecombination of inductanc SI and rea signal is generated, amplified andflashed and sistance N and then to the high voltage source. indicated with extremely small time loss.

The DC. component also flows from ground 1 Although I have shown and described herein or low potential side of power supply to the cathpreferred embodiments of my invention, it is to ode through resistor 85. This current causes the be understood that I do not wish to limit the cathode due to 86' to be at a positive or higher application of the invention thereto. except as voltage than ground. The A. C. component or may be required by the scope of the subjoined signal comp nent passes through condenser 81 15 claim.

and thus to the cathode. Having described the invention, what is claimed The resistance of 95 and N is such that with s e i no si nal impr s ed on the control grid the plate In combination with a fuel injection valve havcurrent causes a voltage to exist acr h ining areciprocatory valve stem, ahousing mounted ductance 0i and resistance 95 which just will not 20 on said valve and including a portion overlying ignite the neon lamp connector across this ele-' the outer end of said valve stem. 1:. rod supported ment. Or the voltage across the inductance iii in said valve ior reciprocation by said stem, a

and resi tan u d y the steady flow of phono-crystal in said housing, saidphono-crystal rr i J ow h isni ion v ltage oi the having an actuating needle projecting therefrom, neon lamp. The resistance 94 provides a load for 25 and m ans operatively connecting said needle and the tube. The inductance 9| may be selected so the outer end of i d, 7

that the resistance inherent to its construction willactasreaistance "a HOWARD M. FULLER. 

